Inorg. Chem. 2005, 44, 6717−6724
195Pt
NMR of Heteropolymetallic Complexes Containing Secondary Dithiooxamides as Binucleating Ligands Santo Lanza,* Giovanna Callipari, Fre´de´rique Loiseau, Scolastica Serroni, and Giuseppe Tresoldi Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Villaggio S. Agata, Salita Sperone 31, 98166 Messina, Italy Received May 9, 2005
Monometallic [Pt{S-S2C2(NR)2H}2] (S-S2C2(NR)2H ) κ2-S,S-S2C2(NR)2H ) bis-dialkyl-dithioxamidate, R ) methyl, isoamyl, benzyl) and binuclear and trinuclear heterobimetallic complexes [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn] (µ-S2C2(NR)2 ) κ2-S,S(Pt)-κ2-N,N(M)-S2C2(NR)2) and [Pt{{µ-S2C2(NR)2}MLn}2] (MLn+ ) [(η3-allyl)palladium]+, [bis(2-phenylpyridine)rhodium]+, [(η6-p-cymene)(chloro)ruthenium]+, [(1,4-cyclooctadiene)rhodium]+, [(pentamethylcyclopentadienyl)(chloro)rhodium]+) have been prepared and characterized. The progressive substitution of the residual amidic hydrogen in the [Pt{S-S2C2(NR)2H}2] complexes with a MLn+ metal fragment results in the deshielding of platinum nuclei, a red shift of the MLCT absorption maximum, and a decrease in the oxidation potential. Such behavior has been interpreted as a progressive electron shift from platinum to the binucleating ligands, the extent of which depends on the nature of MLn+ metal fragment.
Scheme 1
Introduction Heteropolymetallic complexes, in which the electronic communication between metals is propagated via bridging atoms, are of special interest because they can display peculiar photoelectrochemical, electronic, and magnetic properties, and therefore they could be used for molecularbased devices.1 Synthetic strategies to achieve topologically and stereochemically controlled heteropolymetallic systems are based on the use of “metalloligands” (i.e., metal complexes used as ligands).2 These procedures exploit heterotopic ligands already bound to one metal with free coordination sites that can bind a second metal (the same or a different kind of metal). Such ligands allow step-by-step syntheses because of the different reactivities of the various donor sites, which are generally chelating systems. In this context, the oxamato and oximato ligands have been extensively used to generate families of polymetallic compounds via a sequential strategy.3 Another binucleating ligand, 1,10-phenanthroline-5,6dione, has been used as building block for polymetallic * To whom correspondence should be addressed. E-mail: lanza@ chem.unime.it. (1) Balzani, V.; Credi, A.; Venturi, M. Molecular DeVices and Machines: A Journey into the Nano World; Wiley-VCH: Weinheim, Germany, 2003. (2) Newkome, G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999, 99, 1689-1746. (3) Chaudhury, P. Coord. Chem. ReV. 2003, 243, 143-190 and references therein.
10.1021/ic0507215 CCC: $30.25 Published on Web 08/16/2005
© 2005 American Chemical Society
systems; it possesses a bifunctional character and exhibits different reactivities in its functionalities.4 We have favored the strategy of using “metal dithiooxamidate” building blocks as ligands to synthesize various heterometal complexes.5-7 Our objective was to build up linear heteropolymetallic chains of the type C-(B)n-A(B)m-C′ (C may be equal to C′, m g n g 0) through a modular use of bischelate dithioxamide complexes of the type [M{S-S2C2(NR)2H}2] (M ) divalent transition metal ions, R ) alkyl groups) (A in the Scheme 1), monochelate [LnM{S-S2C2(NR)2H}] precursors (B), and nonligating fragments (C). The present paper deals with different series of complexes of types [Pt{S-S2C2(NR)2H}2], [Pt{S-S2C2(NR)2H}{µ-S2C2(4) Fox, G. A.; Bhattacharya, S.; Pierpont, C. G. Inorg. Chem. 1991, 30, 2895-2899. (b) Paw, W.; Eisenberg, R. Inorg. Chem. 1997, 36, 22872293. (c) Liu, H.; Du, M.; Leng, X.; Bu, X. H.; Zhang, R. H. Chin. J. Struct. Chem. 2000, 19, 427-431. (5) Lanza, S.; Bruno, G.; Nicolo`, F.; Scopelliti, R. Tetrahedron: Asymmetry 1996, 7, 3347-3350. (6) Lanza, S.; Bruno, G.; Nicolo´, F.; Rotondo, A.; Scopelliti, R.; Rotondo, E. Organometallics 2000, 19, 2462-2469. (7) Lanza, S.; Bruno, G.; Nicolo`, F.; Callipari, G.; Tresoldi, G. Inorg. Chem. 2003, 42, 4545-4552.
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(NR)2}MLn] and [Pt{{µ-S2C2(NR)2}MLn}2] (S-S2C2(NR)2H) terminal dithiooxamidate; S2C2(NR)2 ) bridging dithiooxamidate; LnM+ ) [Ru(η6-p-Cymene)Cl]+, [(η3-allyl)ClPd]+, [Rh(2-phenylpyridine)2]+, [Rh(cyclooctadiene)]+, [Rh(pentamethylcyclopentadienyl)Cl]+), for which we have demonstrated that peripheral metal fragments [MLn]+ have a strong effect in modifying the electron density on the Pt(II) centers via the bridging dithioxamidate ligand. Even more interestingly, this effect seems to be highly controllable and tunable as a function of the nature of the peripheral metal fragments. Results and Discussion One of the complexes which appears in this paper, [Pt{{µ-S2C2(NR)2}Pd(η3-allyl)}2], has been already synthesized and its properties have been discussed.7 In particular, it has been found that the synthesis of the quoted complex is stereoselective because this trimetallic complex has been prepared as one of the two possible isomers (the endo isomer). It has been proposed that, once the first allylpalladium moiety enters the platinum precursor [Pt{S-S2C2(NR)2H}2] (R ) isoamyl), 1a (Scheme 2), a back-donation mechanism correlates both the palladium and platinum d orbitals through the NCS system of the binucleating ligand. Thus, the second allylpalladium fragment will be forced to interact with the set of platinum d orbitals in a preferred orientation. One could expect the reactivity of the nitrogen-chelating systems in the precursor [Pt{S-S2C2(NR)2H}2] (R ) isoamyl) (1a in the Scheme 2) to be different from the reactivity of the residual chelating system in bimetallic [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}Pd(η3-allyl) κ-N,N-Pd, κ-S,S-Pt], (2a2). Actually, we have successfully synthesized the heterobimetallic compound 2a2 according to Scheme 2, taking advantage of the difference in reactivity between the nitrogen-chelating sites, d N-H‚‚‚Nd of 1a and 2a2. The addition of another allyl palladium fragment to 2a2 produces the trinuclear heterobimetallic species 3a2 (Scheme 2).
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We have observed that the resonances are progressively shifted toward lower fields on going from 1a to 3a2. The deshielding of the platinum nucleus, caused by the progressive substitution of a proton in 1a with a metal fragment having total charge +1, indicates that electron density is transferred from the platinum center to peripheral sites in the 2a2 and 3a2 complexes. In other words, such a deshielding may be considered to be a result of the electronic influence exerted by the [Pd(η3-allyl)]+ fragment on the Pt(II) centers, mediated by the binucleating dithiooxamidate. Therefore, we thought it would be interesting to study 195Pt resonance shifts in several families of bi- and trimetallic complexes synthesized as shown in Scheme 2. For the sake of simplicity, we labeled the mononuclear complexes 1, the binuclear compounds 2, and the trinuclear species 3. Letters and subscript numbers indicate the alkyl substituents of the dithiooxamides and the heterometallic fragments, respectively. The type 1 complexes were synthesized following known procedures8 and characterized by elemental and NMR spectral analysis. The type 2 compounds are new. The NMR data are consistent with their molecular formula. In fact, proton spectra of 2an complexes (n ) 1, 2, 3, 5) show two sets of signals for the N-CH2- protons; those belonging to the alkyl arms near the MLn+ fragment are diastereotopic because of the close proximity of the dissymmetrizing MLn+ group and appear as the AB part of an ABX2 system, while the N-CH2- protons belonging to the alkyl arms far from the MLn+ fragments appear in the spectrum as a triplet. When MLn+ is Rh(COD)+ (2a4), it is possible to distinguish between the near and far N-CH2- protons because the signal of the near group is split by coupling with Rh nucleus. Furthermore, the NOESY TP spectra show cross-peaks between the the AB part of the ABX2 system in 2an (n ) 1, 2, 3, 5) or the split triplet in 2a4 and the signals of the proper protons of the Ln ligands in MLn+ fragments (cymene ring protons, terminal CH2 allyl protons, low field COD protons, pyridine H6 in phenylpyridine groups, and methyl protons in C5Me5 rings). All type 3 compounds have the same topology as the known 3a2 complex (i.e., they consist of two MLn+ metal fragments linked to the nitrogen-chelating systems of a platinum(II)-bis-(dialkyl-dithioxamidate) core). Complexes 3an (n ) 1, 2, 3, 5), 3b1 and 3c1 could exist in two isomeric forms: endo/eso (3a2), meso/rac (3a3), cis/trans (3a1, 3b1, 3c1, and 3a5). As described above, 3a2 can be synthesized only as the endo isomer; 3a3 was prepared as an equimolar meso/rac mixture which could not be resolved, and 3a1, 3b1, 3c1, and 3a5 were obtained as cis/trans mixtures in which one of the two isomers appeared to be present as a minor component. Further column chromatography of the isomeric mixtures provided the major isomer in a pure form for 3a1, 3b1, 3c1, and 3a5. We did not obtain X-ray quality crystals of these latter compounds, and as a consequence, their geometry remains uncertain. (8) Rosace, G.; Bruno, G.; Monsu` Scolaro, L.; Nicolo`, F.; Sergi, S.; Lanza, S. Inorg. Chim. Acta 1993, 208, 59-65.
195Pt
NMR of Heteropolymetallic Complexes
Table 1. 195Pt NMR (δ), Absorption Maxima (λ) and Oxidation Potential (E) for a Variety of Mononuclear, Binuclear, and Trinuclear Platinum Complexes
a
complex
δ (ppm)
λ (nm)
E (V vs SCE)
1a 1b 1c 2a1 2b1 2c1 2a2 2a3 2a4 2a5 3a1 3b1 3c1 3a 3a3 3a4 3a5
110 120 110 316 303 328 254 269 247 301 510 520 530 380 413 364 481
452 457 447 484 493 479 465 460 483 472 511 530 503 476 466 504 489
1.04
0.97
0.97 0.95 0.88 0.98 0.90
0.96 a 0.88 0.99
Adsorbed on the electrode.
It is important to point out that there was very little differences (about 2 ppm) between the platinum shifts of the two isomers and no significant difference between the absorption spectra of the isomeric mixtures and those of the corresponding pure compounds. 195 Pt NMR. We have registered 195Pt NMR spectra for all of the complexes. The observed chemical shifts, expressed in absolute frequency (TMS ) 100 MHz), occur over a range of about 400 ppm, which is large enough to consider 195Pt NMR a sensitive probe of the electronic structure of our mono, bi, and trimetallic complexes. There are several extensive papers on 195Pt chemical shifts. 9-12 Other reports are concerned with 195Pt NMR of platinum complexes containing sulfur ligands,13-15 but to our knowledge, there are no reports which ones refer to dithioxamides either chelated to platinum or bridged between platinum and another metal. The 195Pt NMR results are reported in Table 1. Platinum chemical shifts both in mono- and polynuclear metal complexes depend very little on the nature of alkyl substituent R for a given MLn+ (Table 1). Figure 1 shows 195Pt chemical shifts versus nuclearity for complexes containing the same alkyl substituent (R ) isoamyl) but different heterometallic fragments; it can be seen that each MLn+ fragment shows a specific capacity to attract electrons from platinum. The linear relationships shown in Figure 1 imply that the difference in chemical shift, ∆δ, caused by the linkage of the first MLn+ fragment to one nitrogen-chelating system of the precursor [Pt{S-S2C2(NR)2H}2] has the same value (9) Pregosin, P. S. Coord. Chem. ReV. 1982, 44, 247-291. (10) Goodfellow, R. J. In Multinuclear NMR; Mason, J., Ed.; Plenum Press: New York, 1987; 521. (11) Pregosin, P. S. Annu. Rep. NMR Spectrosc. 1986, 17, 285. (12) Pregosin, P. S. In Transition Metal Nuclear Magnetic Resonance; Pregosin, P. S., Ed.; Elsevier: New York, 1991; 216. (13) Colton, R.; Traeger, J. C.; Tedesco, V. Inorg. Chim. Acta 1993, 210, 193-201. (14) Fazlur-Rahman, A. K.; Verkade, J. G. Inorg. Chem. 1992, 31, 20642069. (15) Keefer, C. E.; Bereman, R. D.; Purrigton, S. T.; Knight, B. W.; Boyle, P. D. Inorg. Chem. 1999, 38, 2294-2302.
Figure 1. 195Pt chemical shifts vs nuclearity in [Pt{S-S2C2(NR)2H}2] (1a), [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn] (2an, n ) 1, 2, 3, 4, 5) and [Pt{{µ-S2C2(NR)2}MLn}2] (3an, n ) 1, 2, 3, 4, 5). Each straight line correlates the mononuclear species (f) with the bi- and trinuclear heterobimetallic complexes in which the alkyl substituent R is the isoamyl group and the heterometallic fragment MLn+ is [Ru(p-cymene)Cl]+(O), [Rh(C5Me5)Cl]+ (b), [Rh(2-phenylpyridine)2]+ (4), [Pd(η3-allyl)]+ (0), or [Rh(COD)]+ (9).
as that observed by linking a second MLn+ fragment to the residual nitrogen-chelating system of the bimetallic species [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn]. In other words, upon coordination of a MLn+ fragment there is an electronic removal from platinum toward MLn+ via the π* systems of the NCS frames in the binucleating dithiooxamide. The observed electronic removal could have been balanced by a π donation from the π system of the dithiooxamide ligand to the empty platinum d orbitals. In such a case, we should have expected the ∆δ value related to the first metalation of precursor 1 to be different from the ∆δ value related to the metalation of the corresponding binuclear complex, 2. Actually, the possibility of a π donation from the bridging dithioxamide to the platinum d orbitals would require a Cd C double bond connecting the two NCS frames, as has already been observed in some dithiolene-platinum(II) complexes.15 A number of X-ray measurements performed on uncoordinated dithioxamides16-18 and their metal complexes 5-8,19,20 have shown that the central C-C bond is always a single bond. The unique exception deals with a tertiary dithioxamide-chelated to an electron-rich metal fragment, in which the ligand is reduced in the dithiolenic form.21 Thus, the S,S-platinum-chelated dithioxamidate cannot behave as a π donor ligand; consequently, each MLn+ fragment produces the same 195Pt ∆δ because the two dithioxamidate ligands do not transmit any electronic effect to each other. As a consequence, the linkage of the MLn+ fragment to the nitrogen-chelating system of the platinum(16) Lanza, S.; Bruno, G.; Monsu` Scolaro, L.; Nicolo`, F.; Rosace, G. Tetrahedron: Asymmetry 1993, 4, 2311-2314. (17) Lanza, S.; Nicolo`, F.; Tresoldi, G. Eur. J. Inorg. Chem. 2002, 10491055. (18) Bruno, G.; Lanza, S.; Nicolo`, F.; Tresoldi, G.; Rosace, G. Acta Crystallogr., Sect. C 2002, 58, o608-o609. (19) Bruno, G.; Lanza, S.; Nicolo`, F.; Tresoldi, G.; Rosace, G. Acta Crystallogr., Sect. C 2002, 58, m316-m318.
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Figure 2. Normalized room-temperature absorption spectra of [Pt{S-S2C2(NR)2H}2] (R ) isoamyl) (plain line, 1a), [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}Pd(η3-allyl)] (R ) isoamyl) (dashed line, 2a2), and [Pt{{µ-S2C2(NR)2}Pd(η3-allyl)}2] (R ) isoamyl), (bold line, 3a2).
chelated dithioxamidate produces a downfield shift of the 195Pt resonance which is independent of the other chelated dithioxamidates linking a further MLn+ fragment. Electronic spectroscopy. The strong absorption bands in the visible region exhibited by all of the type 1 mononuclear complexes (Table 1, Figure 2) have already been assigned to the Pt(dπ)/S(p) f dithiooxamide (π*) CT transition22 on the basis of both the experimental evidence and the structural and electronic similarities between the Pt(II)-dithiooxamide compounds and the Pt(II)-dithiolate complexes.23,24 In all of the type 1 complexes, the visible absorption maximum is accompanied by a shoulder at a slightly higher energy. This higher-energy shoulder could be attributed to the vibrational progression of the main band. The Pt(dπ)/ S(p) f dithiooxamide (π*) CT transitions in mononuclear complexes warrant further comments: the Pt(II) metal ion provides a large electronic coupling between the two chelating sulfur-containing ligands, as demonstrated in the square-planar d8 complexes of Ni(II), Pd(II), and Pt(II).25,26 (20) Girerd, J. J.; Jeannin, S.; Jeannin, Y.; Kahn, O. Inorg. Chem. 1978, 17, 3034-3040. (b) Ye, Q. Y.; Nakano, Y.; Frauenhoff, G. R.; Whitcomb, D. R.; Tagusakawa, F.; Bush, D. H. Inorg. Chem. 1991, 30, 1503-1510. (c) Veit, R.; Girerd, J. J.; Kahn, O.; Robert, F.; Jeannin, J.; El Murr, N. Inorg. Chem. 1984, 23, 4448-4454. (d) Drew, M. G. B.; Kisenyi, J. M.; Willey, G. R. J. Chem. Soc., Dalton Trans. 1982, 1729-1732. (e) Drew, M. G. B.; Kisenyi, J. M.; Willey, G. R.; Wandiga, S. O. J. Chem. Soc., Dalton Trans. 1984, 1717-1721. (f) Drew, M. G. B.; Kisenyi, J. M.; Willey, G. R. J. Chem. Soc., Dalton Trans. 1984, 1723-1726. (g) Antolini, L.; Fabretti, A. C.; Franchini, G.; Menabue, L.; Pellacani, G. C.; Dessein, H. O.; Dommisse, R.; Hofmans, H. C. J. Chem. Soc., Dalton Trans. 1987, 1921-1928. (h) Baggio, R.; Garland, M. T.; Perec, M. J. Chem. Soc., Dalton Trans. 1995, 987-995. (21) Barnard, K. R.; Wedd, A. G.; Ticking, E. R. T. Inorg. Chem. 1990, 29, 891-892. (22) Rosace, G.; Giuffrida, G.; Saitta, M.; Guglielmo, G.; Campagna, S.; Lanza, S. Inorg. Chem. 1996, 35, 6816-6821. (23) Zuleta, J. A.; Bevilacqua, J. M.; Einsenberg, R. Coord. Chem. ReV. 1991, 111, 237-248. (24) Zuleta, J. A.; Bevilacqua, J. M.; Proserpio, D. M.; Harvey, P. D.; Einsenberg, R. Inorg. Chem. 1992, 31, 2396-2404. (25) Vogler, A.; Kunkely, H. Comments Inorg. Chem. 1990, 9, 201-220. (26) McCleverty, J. A. Prog. Inorg. Chem. 1968, 10, 49-221. (b) Burns, R. P.; Mcauliffe, C. A. AdV. Inorg. Chem. Radiochem. 1979, 22, 303348.
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The HOMO in the type 1 complexes is therefore probably well described as being delocalized on both ligands, receiving a contribution from the Pt(dπ) and all the S(p) orbitals. On the other hand, the 195Pt NMR evidence rules out the possibility of an extended electronic coupling between ligands, and therefore, the molecular LUMO will be centered on the amidic moiety of a single DTO ligand and will not be delocalized on the entire molecule. The lower-energy spectrum in Figure 2 (bold line) refers to a typical symmetrical trinuclear heterobimetallic complex (type 3 compounds). Also, in this case, the absorption bands can be assigned to the Pt(dπ)/S(p) f dithiooxamide (π*) CT transition, and the shoulder can be attributed to the vibrational progression of the main band; the lower energy of the transition is probably the result of the destabilization of the HOMO and the stabilization of LUMO caused by the electron redistribution between the metal and the ligands following the progressive metalation of species 1. The dashed spectrum in Figure 2 refers to the bimetallic complex 2a2; it looks like an unresolved broad band. This absorption band can be attributed to two Pt(dπ)/S(p) f dithiooxamide (π*) CT transitions: one with energy similar to that of the mononuclear species and the other one with energy similar to that of the trinuclear species. As a result, maxima and shoulders overlap and an unresolved band appears in the spectrum. In essence, the value of λmax in the electronic spectra of the type 1, 2, and 3 complexes can be considered to be an estimate of the HOMO-LUMO separation. It is known that the main contribution to the shielding of a heavy metal nucleus, such as 195Pt, should be the paramagnetic term defined by Ramsey,27 which was evaluated for d8 platinum complexes by Dean and Green28 who obtained the following expression σp ) -
16 2 -3 β Ca1g2[2Ca2g2∆EA-1 + Ceg2∆E-1] (1) 3
where ∆EA ) E(1A2g - 1A1g) ∆EE ) E(1Ag - 1A1g)
(2)
and Ca1g, Ca2g, and Ceg are the coefficients of the platinum d orbitals. If we make the approximation that Ca1g ≈ Ceg, then the observed chemical shifts should follow the equation δPt ) mλ + c
(3)
where λ is the weighted mean of the reciprocal transition energies (i.e., 1/3(2EA-1 + EE-1)) and c allows for the arbitrary zero used for our shifts. The whole set of data in our hands (i.e., δ vs λmax for all the complexes) fits the significant straight line δPt ) 4.84λ - 2010 (R2 ) 0.647, p < 0.00001, Figure 3). In this graph, one can see several (27) Ramsey, N. Phys. ReV. 1950, 78, 699-703. (28) Dean, R. R.; Green, J. C. J. Chem. Soc. A 1968, 3047-3050. (b) Goggin, P. L.; Goodfellow, R. J.; Haddock, S. R.; Taylor, B. F. Marshall, I. J. Chem. Soc., Dalton Trans. 1976, 459-467.
195Pt
NMR of Heteropolymetallic Complexes
Figure 3. Plot of 195Pt chemical shift vs λ ) 1/3(2∆EA-1 + ∆EE-1) for mononuclear (O), binuclear (4), and trinuclear complexes (0).
Figure 4. Plot of 195Pt chemical shifts vs λ ) 1/3(2∆EA-1 + ∆EE-1) in [Pt{S-S2C2(NR)2H}2] (R ) isoamyl) (1a), [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn] (R ) isoamyl) (2an, n ) 1, 2, 3, 4, 5), and [Pt{{µ-S2C2(NR)2}MLn}2] (R ) isoamyl) (3an, n ) 1, 2, 3, 4, 5). Each straight line correlates the mononuclear species (f) with bi- and trinuclear heterobimetallic complexes in which the heterometallic fragment MLn+ is [Pd(η3-allyl)]+ (0), [Ru(p-cymene)Cl]+(b), [Rh(2-phenylpyridine)2]+ (4), [Rh(COD)]+ (O), and [Rh(C5Me5)Cl]+ (9).
groups of three points, each group representing complexes with the same alkyl substituent (R ) isoamyl) and different MLn+ metal fragments (Figure 4) or complexes with the same metal fragment, [Ru(p-cymene)Cl]+, and different alkyl substituents (Figure 5). In other words, significant straight lines correlate the 195Pt chemical shift versus the weighted mean of the reciprocal transition energies in each family of complexes (1, 2, and 3). The slope of such lines depends on the nature of the MLn+ subunit and shows the redistribution of electrons between the metal and the ligands via the progressive and specific metalation of species 1. In Figure 5, one can see three straight lines with similar slopes
Figure 5. Plot of 195Pt chemical shifts vs λ ) 1/3(2∆EA-1 + ∆EE-1) in [Pt{S-S2C2(NR)2H}2] (1a, 1b, 1c), [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn] (2a1, 2b1, 2c1), and [Pt{{µ-S2C2(NR)2}MLn}2] (3a1, 3b1, 3c1). Each straight line correlates mono, bi-, and trimetallic complexes in which the heterometallic fragment MLn+ is [Ru(p-cymene)Cl]+ and R is methyl (0), isoamyl (b), and benzyl (O).
because they all refer to the progressive linking of the [Ru(p-cymene)Cl]+ frame to three type 1 precursors, [Pt{S-S2C2(NR)2H}2] where R is a methyl, benzyl, or isoamyl group. The plot confirms that the chemical shift is independent of the nature of the R substituent and shows that λmax is dependent on R. The sensitivity of the absorption band energy to the substituents of the dithioxamide moiety is in accordance with the MLCT nature of the measured transition. Electrochemistry. Cyclic voltammetry experiments have shown irreversible processes. The oxidation potentials in the type 2 and 3 compounds were less positive, about 70 mV, than the potential of the monometallic precursor 1a (Table 1). These oxidation processes could be the removal of one electron from the HOMO which, in type 2 and 3 compounds, is less stable than the HOMO of the monometallic precursor. Somewhat lower values (0.88 V) were detected in 2a4 and 3a4, where MLn+ is [Rh(COD)]+. According to the coordinated cyclooctadiene behavior,15 the COD π orbitals in [Rh(COD)]+ can overlap the π* system in the NCS fragments of the bridging dithioxamide, in such a way that a further destabilization of the HOMO occurs, and as a consequence, the electron can be removed more easily. The pattern of electrochemical behavior of our mono-, bi-, and trimetallic complexes is in accordance with both the NMR and absorption spectroscopy results. In fact, the metalation of the nitrogen-chelating systems in the binucleating dithioxamides causes an electronic shift from platinum to the SCN system. Such a shift produces destabilization of the HOMO, mainly centered on the sulfur atoms. As a consequence, deshielding of the 195Pt nuclei, lowering of the HOMO-LUMO transition energies, and eventually, lowering of the oxidation potentials will occur. Inorganic Chemistry, Vol. 44, No. 19, 2005
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Lanza et al. Experimental Section Dithioxamide ligands S2C2(NR)2H2 (R ) methyl, isoamyl, benzyl) were synthesized according to the method of Hurd,29 and the complex cis-Pt(Me2SO)2Cl2 was prepared according to the method of Kukushkin.30 Other reagents were commercially available products used as received. 1H NMR, 13C{1H} NMR, and 195Pt{1H} NMR spectra were recorded at 298 K on a Bruker ARX-300, equipped with a broadband probe operating at 300.13, 75.48, and 64. 23 MHz, respectively. 1H and 13C NMR chemical shifts are reported in ppm (relative to TMS) and are referenced to the residual solvent peak. The 195Pt chemical shifts are reported by use of the absolute frequency (TMS ) 100 MHz). General Procedure for the Synthesis of Bis-dithioxamidato Complexes [Pt{S-S2C2(NR)2H}2] (R ) isoamyl (1a), benzyl (1b), methyl (1c)). S2C2(NR)2H2 (1 mmol) was added to a stirred suspension of cis-Pt(Me2SO)2Cl2 (211 mg, 0.5 mmol) in chloroform (60 mL). The reaction went to completion within 0.5 h at room temperature, and the solution turned purple. Sodium bicarbonate (200 mg) was added, and the solution turned yellow. After the mixture was stirred for 0.5 h, the solution was filtered and concentrated to a small volume (∼10 mL). The solid obtained by addition of petroleum ether 40-60 (∼100 mL) was collected and washed with diethyl ether. 1a. 1H NMR (300.13 MHz, CDCl3, room temp): δ 3.16 (t, 8H, 3J HH ) 6.20 Hz, N-CH2-), 1.65 (m, 12H, N-CH2-CH2-CH(CH3)2), 0.92 (d, 24H, 3JHH ) 6.20 Hz, N-CH2-CH2-CH(CH3)2).13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 179.43 (CS), 47.78 (N-CH2-), 37.50 (N-CH2-CH2-), 26.25 (N-CH2CH2-CH-), 22.40 (N-CH2-CH2-CH-(CH3)2). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 110. Anal. Calcd for C24H46N4PtS4 (MW 713.99): C, 40.37; H, 6.49; N, 7.85. Found: C, 40.45; H, 6.60; N, 7.80. Yield: 90%. 1b. 1H NMR (300.13 MHz, CDCl3, room temp): δ 7.33 (m, 20H, phenyl protons), 4.81 (s, 8H, N-CH2-).13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 184.60 (CS), 135.03 (q-Ph), 128.91 (o-Ph), 128.32 (p-Ph), 128.15 (m-Ph), 51.53 (N-CH2-). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 120. Anal. Calcd for C32H30N4PtS4 (MW 793.95): C, 48.41; H, 3.81; N, 7.06. Found: C, 48.45; H, 3.70; N, 7.26. Yield: 87. 1c. 1H NMR (300.13 MHz, CDCl3, room temp): δ 3.35 (s, 12H, N-CH3). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 183.02 (CS), 47.78 (N-CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 110. Anal. Calcd for C8H14N4PtS4 (MW 489.56): C, 19.63; H, 2.88; N, 11.44. Found: C, 19.71; H, 2.99; N, 11.39. Yield: 89%. General Procedure for the Synthesis of the Binuclear Heterobimetallic Complexes [Pt{S-S2C2(NR)2H}{µ-S2C2(NR)2}MLn] (MLn+ ) [Ru(p-cymene)Cl]+, R ) isoamyl (2a1), benzyl (2b1), methyl (2c1); MLn+ ) [(η3-allyl)Pd]+, R ) isoamyl (2a2); MLn+ ) [Rh(phpy)2]+, R ) isoamyl (2a3); MLn+ ) [Rh(COD)]+, R ) isoamyl (2a4); MLn+ ) [Rh(C5Me5)Cl]+ (2a5)). [Pt{S-S2C2(NR)2H}2] (1 mmol) was added to a solution of [MLnCl]2 (0.5 mmol) in chloroform-methanol (10/1 v/v) (40 mL), and the mixture was allowed to stand for 0.5 h under reflux. After this, the solution was concentrated to 10 mL and purified by column chromatography on alumina with a mixture chloroform-petroleum ether (4/1, v/v) as eluent. The pure product was finally obtained by precipitation (29) Hurd, R. N.; De La Mater, J.; McEleheny, G. C.; Tuner, R. J.; Wallingford, W. H. Org. Chem. 1961, 26, 3980-3987. (30) Kukushkin, Y. N.; Viaz’menskii, Y. E.; Zorina, L. I. Russ. J. Inorg. Chem. 1968, 835-838.
6722 Inorganic Chemistry, Vol. 44, No. 19, 2005
from the addition of petroleum ether 40/60 (about 100 mL) to a concentrated portion (about 10 mL) of the eluate. 2a1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 5.37, 5.12 (2d, unresolved AA′XX′ spin system, 4H, cymene ring protons), 4.40, 3.89 (two double triplets, 4H, ABX2 spin system, 2JHH ) 11.00 Hz, 3JHH ) 6.40 Hz, N-CH2 near ruthenium), 3.58 (t, 4H,3JHH ) 6.40 Hz, N-CH2- far from ruthenium), 2.76 (sl, 1H, 3JHH ) 6.40 Hz, cymene -CH-(CH3)2), 2.32 (s, 3H, cymene CH3), 1.92-1.64 (m, 12H, N-CH2-CH2-CH-(CH3)2), 1.17 (d, 6H, 3JHH ) 6.40 Hz, cymene -CH-(CH3)2), 0.99, 0.98 (2d, 12H, N-CH2-CH2CH-(CH3)2 near ruthenium), 0.91 (d, 12H, N-CH2-CH2-CH(CH3)2 far from ruthenium). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 189.19, 179.81 (CS), 103.64, 100.80 (cymene quaternary carbons), 84.45, 83.53 (other cymene ring carbons), 61.19, 47.69 (N-CH2-), 37.64, 34.98 (N-CH2-CH2-), 31.25 (cymene CH-(CH3)2), 27.01, 26.30 (N-CH2-CH2-CH-), 22.63 (cymene CH-(CH3)2), 22.55, 22.46 (N-CH2-CH2-CH-(CH3)2), 18.99 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 316. Anal. Calcd for C34H59ClN4PtRuS4 (MW 983.73): C, 41.51; H, 6.05; N, 5.70. Found: C, 41.60; H, 6.13; N, 5.63. Yield: 80%. 2b1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 7.55-7.28 (m, 20H, phenyl protons), 5.75, 5.07 (2d, 4H, AB spin system, N-CH2-, near ruthenium), 4.82, 4.67 (2d, 4H, unresolved AA′XX′ spin system, cymene ring protons), 3.46 (s, 4H, N-CH2-, far from ruthenium), 2.07 (sl, 1H, 3JHH ) 6.16 Hz, cymene -CH-(CH3)2), 1.90 (s, 3H, cymene -CH3), 0.84 (d, 6H, 3JHH ) 6.16 Hz, cymene -CH(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 192.78, 180.88 (CS), 136.77 (q-Ph), 128.76-127.60 (o,m,p-Ph), 100.08, 97.82 (cymene quaternary carbons), 82.01, 81.80 (other cymene ring carbons), 65.63, 53.34(N-CH2-), 30.78 (cymene CH-(CH3)2), 22.50 (cymene CH-(CH3)2), 19.05 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl , room temp): δ 303. Anal. 3 Calcd for C42H43ClN4PtRuS4 (MW 1063.69): C, 47.43; H, 4.07; N, 5.27. Found: C, 47.39; H, 4.10; N, 5.38. Yield: 72%. 2c1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 5.45, 5.12 (2d, 4H, unresolved AA′XX′ spin system, cymene ring protons), 3.78 (s, 6H, N-CH3, near ruthenium), 3.30 (s, 6H, N-CH3, far from ruthenium), 2.71 (sl, 1H, 3JHH ) 6.60 Hz, cymene CH(CH3)2), 2.23 (s, 3H, cymene CH3), 1.17 (d, 6H, 3JHH ) 6.60 Hz, cymene CH-(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 189.28, 181.83 (CS), 102.82, 102.34 (cymene quaternary carbons), 84.95, 82.33 (other cymene ring carbons), 48.81, 36.12 (N-CH3), 31.37 (cymene CH-(CH3)2), 22.46 (cymene CH(CH3)2), 19.10 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 328. Anal. Calcd for C18H27ClN4PtRuS4 (MW 759.30): C, 28.47; H, 3.58; N, 7.38. Found: C, 28.31; H, 3.70; N, 7.25. Yield: 75%. 2a2. 1H NMR (300.13 MHz, CDCl3, room temp): δ 5.41, (m, 1H, CH allyl), 3.86-3.69 (m, 4H, N-CH2-, near palladium), 3.61-3.46 (m, 6H, N-CH2-, far from palladium + CH2 allyl syn), 2.92, 2.89 (2d, 2H, 2JHH ) 12.50 Hz, CH2 allyl anti), 1.72-1.38 (m, 12H, N-CH2-CH2-CH-(CH3)2), 0.89-0.87 (m, 24H, 3JHH ) 6.20 Hz, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48, CDCl3, room temp): δ 190.94 (CS), 115.31 (CH allyl), 57.69 (CH2 allyl), 57.19, 47.74 (N-CH2-), 37.63, 36.87 (N-CH2-CH2-), 26.59, 26.30 (N-CH2-CH2-CH), 22.77, 22.40 (N-CH2-CH2CH-(CH3)2). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 250. Anal. Calcd for C27H50N4PdPtS4 (MW 860.46): C, 37.69; H, 5.86; N, 6.51. Found: C, 37.73; H, 5.92; N, 6.43. Yield: 76%. 2a3. 1H NMR (300.13 MHz, CDCl3, room temp): δ 8.10 (d, 2H, Jo ) 5.70 Hz, pyridyl H6), 7.80 (m, 2H, pyridyl H4), 7.78 (m, 2H, pyridyl H3), 7.51 (d, 2H, Jo ) 7.20 Hz, phenyl H3′), 7.12 (m,
195Pt
NMR of Heteropolymetallic Complexes
2H, pyridyl H5), 6.84 (t, 2H, Jo ) 7.20 Hz, phenyl H4′), 6.73 (t, 2H, Jo ) 7.20 Hz, phenyl H5′), 6.09 (d, 2H, Jo ) 7.20 Hz, phenyl H6′), 3.55 (t, 4H, N-CH2-, far from rhodium), 3.50-3.39 (m, 4H, N-CH2-, near to rhodium), 1.67-1.13 (m, 8H, N-CH2-CH2), 1.07-0.95 (m, 4H, N-CH2-CH2-CH-), 0.88 (d, 12H, 3JHH ) 6.70 Hz, N-CH2-CH2-CH-(CH3)2, far from rhodium), 0.41, 0.37 (2d, 12H, 3JHH ) 6.70 Hz, N-CH2-CH2-CH-(CH3)2, near rhodium). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 185.09, 180.16 (CS), 170.63 (phenyl C1′), 165.58 (pyridyl C2), 150.17 (pyridyl C6), 143.29 (phenyl C2′), 137.08 (pyridyl C4), 132.24 (phenyl C6′), 129.56 (phenyl C5′), 123.50 (phenyl C3′), 122.50 (pyridyl C5), 122.35 (phenyl C4′), 118.73 (pyridylC3), 53.37, 47.74 (N-CH2-), 37.70, 34.65 (N-CH2-CH2-), 26.37 (N-CH2-CH2CH-), 22.48, 22.00 (N-CH2-CH2-CH-(CH3)2). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 266. Anal. Calcd for C46H61N6PtRhS4 (MW 1124.27): C, 49.14; H, 5.47; N, 7.48. Found: C, 48.93; H, 5.52; N, 7.43. Yield: 72%. 2a4. 1H NMR (300.13 MHz, CDCl3, room temp): δ 3.93 (bs, 4H, COD CH), 3.58 (t, 4H, N-CH2-, far from rhodium), 3.06 (m, 4H, N-CH2-, near rhodium), 2.43 (m, 4H, COD CH2), 1.86 (m, 4H, COD CH2), 1.65-1.50 (m, 12H, N-CH2-CH2-CH-), 0.91-089 (m, 24H, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48, CDCl3, room temp): δ 192.35, 179.85 (CS), 82.88 (d, JRhC ) 12.08 Hz, CH COD), 50.54, 47.76 (N-CH2-), 37.68, 35.63 (N-CH2-CH2-), 30.68 (CH2 COD), 27.04, 26.31 (N-CH2CH2-CH-), 22.53, 22.49 (N-CH2-CH2-CH-(CH3)2). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 243. Anal. Calcd for C32H57N4PtRhS4 (MW 924.07): C, 41.59; H, 6.22; N, 6.06. Found: C, 41.70; H, 6.23; N, 5.99. Yield: 71%. 2a5. 1H NMR (300.13 MHz, CDCl3, room temp): δ 4.33, 3.69 (two double triplets, 4H, ABX2 spin system, 2JHH ) 13.79 Hz, 3JHH ) 6.60 Hz, N-CH2, near rhodium), 3.54 (t, 4H, 3JHH ) 6.60 Hz, N-CH2-, far from rhodium), 1.67 (m, 12H, N-CH2-CH2-CH), 1.56 (s, 15H, cyclopentadienyl CH3), 0.91, 0.88 (2d, 24H, 3JHH ) 6.62 Hz, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48, CDCl3, room temp): δ 191.06, 179.90 (CS), 94.81 (d, JRhC ) 7.40 Hz, cyclopentadienyl ring carbons), 57.02, 47.70 (N-CH2-), 37.70, 34.72 (N-CH2-CH2-), 27.15, 26.31 (N-CH2-CH2-CH-), 22.65, 22.54 (2s, N-CH2-CH2-CH-(CH3)2, near rhodium), 22.48 (N-CH2-CH2-CH-(CH3)2, far from rhodium), 9.01 (C5(CH3)5). 195Pt{1H} NMR (64.23 MHz, CDCl , room temp): δ 295. Anal. 3 Calcd for C34H60ClN4PtRhS4 (MW 986.57): C, 41.39; H, 6.13; N, 5.68. Found: C, 41.50; H, 6.19; N, 5.57. Yield: 78%. General Procedure for the Synthesis of the Trinuclear Heterobimetallic Complexes [Pt{{µ-S2C2(NR)2}MLn}2] (MLn+ ) [Ru(p-cymene)Cl]+, R ) isoamyl (3a1), benzyl (3b1), methyl (3c1); MLn+ )[(η3-allyl)Pd]+, R ) isoamyl (3a2); MLn+ ) [Rh(phpy)2]+, R ) isoamyl (3a3); MLn+ ) [Rh(COD)]+, R ) isoamyl (3a4); MLn+ ) [Rh(C5Me5)Cl]+ (3a5)). [Pt{S-S2C2(NR)2H}2] (1 mmol) was added to a solution of [MLnCl]2 (1 mmol) in chloroform-methanol (10/1 v/v, 40 mL). After the mixture was refluxed for 0.5 h, the solution was concentrated to 10 mL and purified by chromatography on alumina with a mixture chloroformpetroleum ether (4/1, v/v) as eluent. The products was obtained by precipitation from the addition of petroleum ether 40/60 (about 100 mL) to a concentrated portion (about 10 mL) of eluates. 3a1, 3b1, 3c1, and 3a5 were isomeric mixtures in which one of the two isomers (cis or trans) appeared as a major component. For these compounds, a further column chromatography in which only the first fraction of the eluate was collected to give a pure isomer. 3a1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 5.33, 5.09 (2d, 8H, unresolved AA′XX′ spin system, cymene ring protons), 4.37, 3.85 (2m, 8H, ABX2 spin system, 2JHH ) 11.28 Hz, 3JHH )
5.20 Hz), 2.72 (seven lines, 2H, 3JHH ) 5.20 Hz, cymene CH(CH3)2), 2.20 (s, 6H, cymene CH3), 1.90, 1.66 (2m, 12H, N-CH2CH2-CH-), 1.16 (d, 12H, 3JHH ) 5.20, cymene CH-(CH3)2), 0.96 (d, 24H, 3JHH ) 6.19, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 189.67 (CS), 103.32, 100.64 (cymene C1,4), 84.29, 83.37 (cymene C2,3,5,6), 60.96 (N-CH2-), 34.92 (N-CH2-CH2-), 31.20 (cymene CH-(CH3)2), 27.00 (NCH2-CH2-CH-), 22.68 (cymene CH-(CH3)2), 22.60 (N-CH2CH2-CH-(CH3)2), 18.95 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 510. Anal. Calcd for C44H72Cl2N4PtRu2S4 (MW 1253.47): C, 42.16; H, 5.79; N, 4.47. Found: C, 42.35; H, 5.62; N, 4.50. Yield: 35%. 3b1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 7.54-7.27 (m, 20H, phenyl protons), 5.67, 5.01 (2d, 4H, AB spin system), 4.80, 4.65 (2d, unresolved AA′XX′ spin system, 8H, cymene ring protons), 2.05 (seven lines, 2H, 3JHH ) 6.96 Hz, cymene CH(CH3)2), 1.89 (s, 6H, cymene CH3), 0.88 (d, 12H, cymene CH(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 189.11 (CS), 136.91 (phenyl q-Ph), 128.62-127.75 (o,m,p-Ph), 96.05, 90.80 (cymene C1,4), 81.87, 81.80 (cymene C2,3,5,6), 65.40 (NCH2-), 30.76 (cymene CH-(CH3)2), 22.54 (cymene CH-(CH3)2), 18.98 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 520. Anal. Calcd for C52H56Cl2N4PtRu2S4 (MW 1333.43): C, 46.84; H, 4.23; N, 4.20. Found: C, 46.80; H, 4.42; N, 4.30. Yield: 30%. 3c1. 1H NMR (300.13 MHz, CDCl3, room temp): δ 5.42, 5.08 (2d, unresolved AA′XX′ spin system, 8H, cymene ring protons), 3.73 (s, 12H, N-CH3), 2.67 (seven lines, 2H, 3JHH ) 6.61 Hz, cymene CH-(CH3)2), 2.20 (s, 6H, cymene CH3), 1.15 (d, 12H, 3J 13 1 HH ) 6.61 Hz, cymene CH-(CH3)2). C{ H} NMR (75.48 MHz, CDCl3, room temp): δ 189.46 (CS), 103.04, 102.36 (cymene C1,4), 84.89, 83.38 (cymene C2,3,5,6), 48.92 (N-CH3), 31.40 (cymene CH(CH3)2), 22.52 (cymene CH-(CH3)2), 19.04 (cymene CH3). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 550. Anal. Calcd for C28H40Cl2N4PtRu2S4 (MW 1029.03): C, 32.68; H, 3.92; N, 5.44. Found: C, 32.65; H, 4.02; N, 5.59. Yield: 28%. 3a2. 1H NMR, 13C NMR, and analysis already reported.3 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 381. 3a3. 1H NMR (300.13 MHz, CDCl3, room temp): δ 8.16 (d, 4H, Jo ) 6.00 Hz, pyridine H6), 7.81 (m, 8H, pyridine H3,4), 7.53 (d, 4H, Jo ) 7.50 Hz, phenyl H3′), 7.14 (m, 4H, pyridine H5), 6.85 (m, 4H, phenyl H4′), 6.74 (m, 4H, phenyl H5′), 6.11 (d, 4H, Jo ) 7.30 Hz, phenyl H6′), 3.44 (m, 8H, N-CH2-), 1.23 (m, 8H, N-CH2-CH2-), 1.01 (m, 4H, N-CH2-CH2-CH-), 0.37, 0.34, 0.33 (4d, two overlapped, 24 H, 3JHH ) 6.47 Hz, N-CH2-CH2CH-(CH3)2, meso and rac isomers). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 186.12 (CS), 170.70 (phenyl C1′), 165.23 (pyridine C2), 150.24 (pyridine C6), 143.23 (phenyl C2′), 136.80 (pyridine C4), 132.20 (phenyl C6′), 129.30 (phenyl C5′), 123.30 (phenyl C3′), 122.20 (pyridine C5), 122.00 (phenyl C4′), 118.50 (pyridine C3), 53.27 (N-CH2-), 34.50 (N-CH2-CH2-), 26.30 (N-CH2-CH2-CH-), 22.80, 22.00 (N-CH2-CH2-CH-(CH3)2). 195Pt{1H} NMR (64.23 MHz, CDCl , room temp): δ 413, 414 3 (meso and rac isomers). Anal. Calcd for C68H76N8PtRh2S4 (MW 1534.56): C, 53.22; H, 4.99; N, 7.30. Found: C, 53.29; H, 5.02; N, 7.41. Yield: 70%. 3a4. 1H NMR (300.13 MHZ CDCl3): δ 3.90 (broad singlet, 8H, COD CH ), 3.08 (m, 8H, N-CH2), 2.41 (m, 8H, COD CH2), 1.84 (m, 8H, COD CH2), 1.54 (m, 12H, N-CH2-CH2-CH-), 0.86 (d, 24H, 3JHH ) 6.10 Hz, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 194.43 (CS), 82.88 (d, JRh-C ) 12.08 Hz, COD CH), 50.44 (N-CH2-), 35.62 (N-CH2-CH2), 30.67 (COD CH2), 27.01 (N-CH2-CH2-CH-), 22.54 (NInorganic Chemistry, Vol. 44, No. 19, 2005
6723
Lanza et al. CH2-CH2-CH-(CH3)2). NMR (64.23 MHz, CDCl3, room temp): δ 364. Anal. Calcd for C40H68N4PtRh2S4 (MW 1534.56): C, 42.36; H, 6.04; N, 4.94. Found: C, 42.38; H, 5.98; N, 5.01. Yield: 79%. 3a5. 1H NMR (300.13 MHz, CDCl3, room temp): δ 4.36, 3,69 (2m, 8H, ABX2 spin system, N-CH2-), 1.83-1.63 (m, 12H, N-CH2-CH2-CH-), 1.59 (s, 30H, cyclopentadienyl CH3), 0.93 (d, 24H, 3JH-H ) 6.30 Hz, N-CH2-CH2-CH-(CH3)2). 13C{1H} NMR (75.48 MHz, CDCl3, room temp): δ 189.81 (CS), 94.60 (d, 195Pt{1H}
6724 Inorganic Chemistry, Vol. 44, No. 19, 2005
JRhC ) 7.40 Hz, cyclopentadienyl ring carbons), 56.97 (N-CH2), 34.73 (N-CH2-CH2-), 27.14 (N-CH2-CH2-CH-), 22.71, 22.50 (N-CH2-CH2-CH-(CH3)2), 8.99 (cyclopentadienyl methyl carbons). 195Pt{1H} NMR (64.23 MHz, CDCl3, room temp): δ 481. Anal. Calcd for C44H74Cl2N4PtRh2S4 (MW 1259.15): C, 41.97; H, 5.92; N, 4.45. Found: C, 41.80; H, 6.01; N, 4.47. Yield: 77%. IC0507215
